There is a bug with UI that makes frame generation look glitchy. On the top center of the screen most of the time is visible shadow that is probably part of the UI for showing some text. Sometimes it is not there for a while but keeps showing back. It is hard to see without frame generation enabled (shadow is very subtle). With frame gen it is very visible, making it glitch in this area (showing only real frames?). I see it with xess fg enabled but it is probably the same for users with dlssg.